This disclosure relates generally to a drive arrangement for a turbomachine. More particularly, this disclosure relates to an arrangement that drives the turbomachine during a first mode of operation and generates electric power using the turbomachine in a second mode of operation.
Turbomachines, such as gas turbine engines are known. A typical turbomachine includes multiple sections, such as a fan section, a compression section, a combustor section, and a turbine section. Many turbomachines, particularly gas turbine engines, have large rotors in the compression section that must be accelerated to high rotational speeds until the rotor is rotating fast enough to sustain operation of the turbomachine. Typically, a motor separate from the turbomachine drives an input shaft that is used to accelerate the rotors.
Many turbomachines use generators to produce electric power for various components, such as components on an aircraft. Some turbomachines use generators separate from the motor that drives the rotors. Integrated drive generators (IDGs) are an example of this type of generator, which can produce constant frequency electric power. As can be appreciated, the generator separate from the motor undesirably adds weight and complexity to the turbomachine.
Other turbomachines use the motors as generators after the turbomachine is self-sustaining. The turbomachine drives these generators. A variable frequency starter generator (VFSG) is an example of this type of generator. VFSGs generate electric output power with a frequency that is proportional to the turbomachine speed. Electrical usage equipment must then be capable of operating under this variable frequency input, which generally increases their weight, envelope, power losses, and cost. Some arrangements of this type include complicated shafting, gearing, clutching, or valving to enable both start and generate modes of operation.